Researchers found that the expressions people pull when they are frightened enlarge their visual field whilst simultaneously signalling to others around them where to look for threats.

Therefore the expressions are functional in ways that directly benefit both the person who makes the expression and the person who observes it, it is claimed.

The findings show that widened eyes provide a wider visual field which can help us to locate potential threats in our environment.

These widened eyes also help to send a clearer gaze signal telling observers to “look there” – which may enhance their ability to locate the same threat, as well.

Psychology graduate student Daniel Lee, who conducted the research with his advisor Doctor Adam Anderson at the University of Toronto in Canada, said: “Emotional expressions look the way they do for a reason.